Can you please solve these problems

Question 3: Let r(t) paramatrize a curve in R, (a) (5 points) Suppose that r(t) is orthogonal to r'(t) for all t. Show that |r()| is constant. (b) (5 points) Conversely, suppose that |r()| is constant. Show that r() is orthogonal to r'(t) for all